More compact and higher reliability power supply module

ABSTRACT

This invention features a more compact and higher reliability power supply module including a high voltage DC input, a low voltage DC output, a number of DC/DC converters connected in parallel between the high voltage DC input and the low voltage DC output, and a controller configured to modulate each DC/DC converter to convert the high voltage DC input to the low voltage DC output.

RELATED APPLICATIONS

This application claims priority of U.S. Provisional Application No.60/545,444 filed Feb. 18, 2004 and U.S. Provisional Application Ser. No.60/545,461 filed Feb. 18, 2004. All of these applications areincorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to a more compact and higher reliability powersupply module.

BACKGROUND OF THE INVENTION

In a typical installation of a telecommunications system, datacommunications system, computer equipment, servers, and the like, poweris almost always supplied by a massive rechargeable storage batterysystem with sufficient capacity to carry the system through any poweroutages or interruptions. The battery system is completely clamped atthe sum of individual cell voltages and any primary power interruptionsare completely bridged. Hence, any powerline-frequency ripple comingfrom the external source is completely absorbed. The battery system cansupply the equipment with the DC voltage and can completely isolate anyequipment attached thereto from utility outages, ripple, and otherproblems with the external power source. Battery drain is kept small bya charging current that is continuously furnished from an external highvoltage AC source, such as a utility main line or an uninterruptablepower supply (UPS). The system chooses between the utility source or theUPS with a static transfer switch. The high voltage AC output from thestatic transfer switch is then input to a transformer/rectifier devicethat supplies the needed charging current. However, conventional statictransfer switches and transformer/rectifier devices typically provide noredundancy capabilities. Hence, failure of one of the components ofthese devices requires shutting the device down to replace the damagedcomponent. Because the battery system is no longer being charged, it cansustain the system only for a limited number of hours, after whichfailure of the battery supplied power will result.

Conventional battery systems typically distribute the DC power atvoltages close to the final application voltages. Since losses areproportional to current squared times the resistance (I²R), keeping I²Rlosses down has required conventional battery systems to employexpensive, bulky, and not readily reconfigurable, bus-bar currentdistribution systems to carry the high current, low voltage DC powerclose to the point of use.

In the past, the conventional battery based systems have been adequate.However, the recent explosion in demand for data communications andcomputer services makes the shortcomings of battery based systems clear.Prior battery based systems are expensive, massive, inflexible andoccupy too much space. Moreover, the environmental hazards associatedwith the toxic waste created during battery manufacturing and disposalare increasingly intolerable.

To date, high voltage DC power distribution has been impractical becauseof the lack of an economical and scalable DC-DC voltage down-converter.Very large Ultra HVDC converters have been in use for many years, butthey require gigantic installations and are completely unsuited toscaling down for the purpose of distributing DC power at commondistribution voltages needed for a telecommunications system or a datacommunication system.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a more compactand higher reliability power source system for computing loads.

It is a further object of this invention to provide such a power sourcesystem that provides low voltage DC without the need for a large andexpensive central battery system.

It is a further object of this invention to provide such a power sourcesystem which eliminates the need for a bulky, massive, inflexible andexpensive bus-bar current distribution system.

It is a further object of this invention to provide such a power sourcesystem in the low voltage DC can be delivered close to the point ofintended use.

It is a further object of this invention to provide such a power sourcesystem which provides redundancy capabilities to improve reliability.

It is a further object of this invention to provide such a power sourcesystem in which the primary components of the system can be removed,replaced, or added to the system while the system is running.

It is a further object of this invention to provide such a power sourcesystem in which the primary components are hot swappable.

It is a further object of this invention to provide such a power sourcesystem which improves the ratio of the distribution voltage to finalapplication voltage.

It is a further object of this invention to provide such a power sourcesystem which is less expensive.

It is a further object of this invention to provide such a power sourcesystem which utilizes less space.

It is a further object of this invention to provide such a power sourcesystem which can easily be physically or electrically reconfigured.

It is a further object of this invention to provide such a power sourcesystem which eliminates the toxic environmental problems associated withutilizing a battery based system.

This invention results from the realization that a more compact andhigher reliability power source system for providing low voltage DCvoltage to computing loads can be effected by the unique combination ofa high voltage DC bus that is connected to a number of DC sources thatare each connected to the high voltage DC bus by a switch that deliversthe DC source with the highest voltage to the high voltage DC bus, a lowvoltage DC bus connected to computing loads, and a power supply thatincludes a number of DC/DC converters connected in parallel between thehigh voltage DC bus and the low voltage DC bus that includes acontroller for modulating each of the DC/DC converters to convert thehigh voltage on the high voltage DC bus to a low voltage DC output onthe low voltage DC bus.

The subject invention, however, in other embodiments, need not achieveall these objectives and the claims hereof should not be limited tostructures or methods capable of achieving these objectives.

This invention features a more compact and higher reliability powersupply module including a high voltage DC input, a low voltage DCoutput, a number of DC/DC converters connected in parallel between thehigh voltage DC input and the low voltage DC output, and a controllerconfigured to modulate each DC/DC converter to convert the high voltageDC input to the low voltage DC output.

In one embodiment, each DC/DC converter may be configured as a buckconverter with a switch cycled by the controller to modulate the DC/DCconverter. Each DC/DC converter may include an inverter, a transformerand a rectifier in which the inverter is cycled by the controller tomodulate the DC/DC converter. The controller may be configured tostagger the triggering of the switch of each DC/DC converter to reduceripple on the low voltage DC bus. The controller may be configured tostagger the triggering of the inverter of each DC/DC converter to reduceripple on the low voltage DC bus. The controller may be configured tomodulate each DC/DC source to control output voltage or current. Thecontroller may be responsive to a fault signal input and programmed toopen the switch of each DC/DC converter in response to the fault signal.The controller may be responsive to a fault signal input and programmedto open the inverter of each DC/DC converter in response to the faultsignal. The controller may be further configured to output an errorsignal in response to a fault signal. The power supply module mayinclude a fuse between the plurality of DC/DC converters and the lowvoltage DC bus designed to fail at a current level greater than therated current output of the power supply module. The controller may beconfigured to determine a desired output voltage based on the currentoutput by the power supply module. The controller may include aswitching voltage regulator configured to compare a desired systemoutput voltage with the voltage level output by the power supply moduleand to adjust the voltage output by each DC/DC converter such that theoutput of the power supply module approximately equals the desiredsystem output voltage. The switching voltage regulator may adjust thevoltage output by each of the DC/DC converters by modulation. Thecontroller of the power supply module may utilize pseudo-impedance toprovide autonomous load sharing with other power supply modules. The lowvoltage DC output may be in the range of about 6V DC to 100V DC. The lowvoltage DC output may be about 48V DC. The power supply module mayfurther include a fault determination circuit for generating the faultsignal. The power supply module may further include a cooling system forcooling the power module. The fault detection circuit may generate afault signal when the power supply module exceeds a predeterminedtemperature. The buck converter may include an input capacitor, aninductor, an output capacitor and the switch. The power supply modulemay be configured in a removable drawer. The removable drawer may bedisposed in a cabinet configured as a power source system. Eachremovable drawer may include a plurality of different length connectorsthat electrically connect the number of DC/DC converters of the powersupply module to the high voltage DC bus at different times to reduceelectrical discharge. The removable drawer may be able to be removed,replaced, or added to the power source system while the power sourcesystem is operating. Each of the connectors may include a resistivematerial for reducing electrical discharge when connecting the powersupply module to the high voltage DC bus. Each removable drawer mayinclude an auxiliary contact connected by a separate auxiliary resistoror spark-suppressing impedance network to reduce electrical discharge.

This invention also features a more compact and higher reliability powersupply module including a high voltage DC input, a low voltage DCoutput, a number of DC/DC converters connected in parallel between thehigh voltage DC input and the low voltage DC output, and a controllerconfigured to modulate each DC/DC converter to convert the high voltageDC input to the low voltage DC output, wherein each DC/DC converter isconfigured as a buck converter with a switch cycled by the controller tomodulate the DC/DC converter.

In one embodiment, the controller may be configured to stagger thetriggering of the switch of each DC/DC converter to reduce ripple on thelow voltage DC bus.

This invention further features a more compact and higher reliabilitypower supply module including a high voltage DC input, a low voltage DCoutput, a number of DC/DC converters connected in parallel between thehigh voltage DC input and the low voltage DC output, and a controllerconfigured to modulate each DC/DC converter to convert the high voltageDC input to the low voltage DC output, wherein each DC/DC converterincludes an inverter, a transformer and a rectifier in which theinverter is cycled by the controller to modulate the DC/DC converter.

In one embodiment, the controller may be configured to stagger thetriggering of the inverter of each DC/DC converter to reduce ripple onthe low voltage DC bus.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages will occur to those skilled inthe art from the following description of a preferred embodiment and theaccompanying drawings, in which:

FIG. 1 is a schematic block diagram of a typical conventional batterysystem for delivering low voltage DC to computing loads;

FIG. 2 is a schematic block diagram of one embodiment of the morecompact and higher reliability power source system of this invention;

FIG. 3 is a schematic block diagram showing the components of oneembodiment of the power supply shown in FIG. 2;

FIG. 4 is a schematic block diagram showing in detail the primarycomponents of a power supply module shown in FIG. 3;

FIG. 5 is an electrical circuit diagram of a buck converter that may beemployed in each of the DC/DC converters shown in FIG. 4;

FIG. 6 is an electrical circuit diagram of an inverter, transformer andrectifier that may be employed in each of the DC/DC converters shown inFIG. 4;

FIG. 7 is an electrical circuit diagram showing one embodiment of thecontroller shown in FIG. 4;

FIG. 8 is a graph showing the output V-I characteristic of the controlcircuit shown in FIG. 7;

FIG. 9 is a three-dimensional schematic view showing one example of thepower supply shown in FIG. 3 configured in a cabinet and the powersupply modules shown in FIG. 4 configured as removable drawers in thecabinet;

FIG. 10 is a three-dimensional schematic view showing further detailsassociated with the primary components of a removable drawer shown inFIG. 9; and

FIG. 11 is a schematic three-dimensional view showing one example of theconnectors that may be used to connect the removable drawers shown inFIG. 9 to a high voltage DC bus.

PREFERRED EMBODIMENT

Aside from the preferred embodiment or embodiments disclosed below, thisinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Thus, it is to be understood that theinvention is not limited in its application to the details ofconstruction and the arrangements of components set forth in thefollowing description or illustrated in the drawings. If only oneembodiment is described herein, the claims hereof are not to be limitedto that embodiment. Moreover, the claims hereof are not to be readrestrictively unless there is clear and convincing evidence manifestinga certain exclusion, restriction, or disclaimer.

As discussed in the Background section above, conventional power sourcesystem 10, FIG. 1, utilizes large battery system 12 to provide lowvoltage DC, e.g., 48V DC, to computing loads 14, such as datacommunications equipment, computer systems, and the like. System 10typically includes static transfer switch 16 responsive to a highvoltage AC source on line 18 delivered by a conventional utility line ora high voltage AC source delivered by a UPS or similar device on line 20in the event of a power failure. Static transfer switch 16 deliverseither the high voltage AC source from the utility line or the UPS byline 17 to transformer/rectifier device 22. Transformer/rectifier device22 provides the necessary charging current to continually charge thebatteries in battery system 12. However, as discussed above, batterysystem 12 and its associated high current, low voltage DC bus 13 aretypically massive in size. Moreover, system 10 provides no redundancyfor any of the components for static transfer switch 16 ortransformer/rectifier device 22.

In contrast, a more compact and higher reliability power source system30, FIG. 2 in accordance with this invention, includes high voltage DCbus 32 connected to a number of high voltage DC sources, such as DCsource 34 (e.g., utility source 1), DC source 36 (e.g., utility source2), DC source 38 (e.g., a generator), and DC source 40 (e.g., anauxiliary source). High voltage DC sources 34-40 are typically at about550V DC. DC sources 34-40 are each connected to high voltage DC bus 32with a switch, e.g., a diode, that is configured to deliver to highvoltage bus 32 power from the DC source with the highest DC voltage. Inthis example, switches 42,44, 46 and 48 connect DC sources 34, 36, 38and 40, respectively, to high voltage DC bus 32. In operation, when thevoltage on any of DC sources 34-40 is greater than the voltage on highvoltage DC bus 32, the switch (diode) associated with the DC source withthe highest voltage is forward biased and the high voltage DC voltagewill be supplied from that source. The switches for the remaining DCsources will be back-biased by the small negative differential voltagesdeliberately or accidentally introduced between the voltages from thosesources and voltage of the highest-voltage source, and hence no powerwill be delivered by those sources. If, however, the active source failsor its voltage drops below any of the other power sources, power willinstantaneously and automatically be drawn from the new highest voltagesource. High voltage DC bus 32 is typically distributed throughout atypical installation of system 30 and provides for connecting powersupply 64 close to the point of intended use (discussed below).

System 30 also includes low voltage DC bus 60 connected to computingloads 62, e.g., telecommunications equipment, data communicationsequipment, computer equipment, servers, and the like, or any electronicdevice or system that utilizes low voltage DC. Typically, the voltage onlow voltage DC bus 60 is in the range of about 6V DC to 100V DC, e.g.,about 48V DC.

Power supply 64 includes a number of DC/DC converters (discussed below)connected in parallel between high voltage DC bus 32 and low voltage DCbus 60 and a controller (also discussed below) configured to modulateeach DC/DC converter to convert the high voltage on high voltage DC bus32 to a low voltage output on low voltage DC bus 60.

In a preferred embodiment, power supply 64, FIG. 3, includes a pluralityof power supply modules, e.g., power supply modules 66, 68, 70, 72, 74,and 76 that each include a plurality of DC/DC converters and acontroller. For example, each power supply module 66-76 includes DC/DCconverters 150, 152, 154, 156, 158 and 160, FIG. 4, that are connectedin parallel between high voltage DC bus 32 and low voltage DC bus 60.Connector 81 connects the high voltage DC on line 101 from high voltagebus 32 to each of DC/DC converters 150-160 by lines 103, 105, 107, 109,111, and 113, respectively. Controller 80 modulates each of DC/DCconverters 150-160 by lines 220, 222, 224, 226, 228 and 230 to convertthe high voltage DC on lines 103-113 to low voltage DC on lines 96, 98,100, 102, 104 and 106. Connector 117 connects the output of DC/DCconverters 150-160 on lines 96-106 to line 90.

The result is that low voltage DC is supplied to low voltage DC bus 60,FIG. 2, without the need for a massive and cumbersome battery system.Each of power supply modules 66-76, FIG. 3 are relatively small in size,e.g., 19″ by 5″ by 24″, for a typical 30 kW power supply module, whichresults in power supply 64 being compact. Because power supply 64 iscompact and utilizes high voltage DC from high voltage DC bus 32 thatcan be distributed throughout an installation of system 30, power supply64 can be located close to the point of intended use. Hence, the needfor a large and expensive low-voltage, high-current bus-distributionsystem is eliminated. This allows a higher ratio of the DC voltage onthe high voltage DC bus 32 to final application voltage on low voltageDC bus 60 that is the range of about 1.1:1 to 1000:1, e.g., 10:1 or 2:1.A higher bus voltage translates through Ohm's law to a proportionallylower current for the same power. Using a higher voltage input power busdistribution system (high voltage DC bus 32) therefore reduces I²Rlosses in the high voltage bus 32, which further reduces energy usageand costs. System 30 can also utilize a number of independent highvoltage DC sources discussed above and automatically uses the DC sourcewith the highest DC voltage, which improves the reliability. System 30also has redundancy capabilities (discussed below) which provideincreased uninterruptability and reliability. System 30 can also berelocated as needed, and can be connected in parallel with any number ofpower source systems 30 as needed to meet any changing load physicalconfigurations or electrical requirements.

In one design, fuse 119, FIG. 4, is connected between the output voltageof the power supply module on line 90 and the low voltage DC bus by line121. Fuse 119 is designed to fail when the current level output by thepower supply module is greater than the rated current output of thepower supply module, e.g., 600 amps.

Each of the DC converters 150-160, FIG. 4 is typically configured as abuck converter, as shown by buck converter 84, FIG. 5. Buck converter 84includes input capacitor 210, diode 212, inductor 214 and outputcapacitor 216 and switch 86, e.g., an insulated gate bipolar transistor(IGBT). Switch 86 is triggered by controller 80, FIG. 4, to modulate thevoltage output of the buck converter of each of DC/DC sources 150-160and convert the high voltage DC on lines 103-113 to low voltage DC onlines 98-106. For example, controller 80 may utilize fixed clockmodulation, e.g., pulse width modulation, to generate pulse widthsignals on lines 220-230 that time how long each switch of each buckconverter of DC/DC converters 150-160 will remain open and closed inorder to adjust the ratio of the “on” time and “off” time of the switchof the buck converter to control the output voltage and effectivelyconvert the high voltage DC on lines 103-113 to low voltage DC on lines96-106 and control the output voltage of the power supply module on line90. Controller 80 may utilize fixed clock modulation, e.g., pulse widthmodulation, self-oscillation modulation, e.g., pulse frequencymodulation or hysteretic modulation, or any type of modulation known tothose skilled in the art, to control the timing of the switches in DC/DC150-160 to convert the high voltage DC to low voltage DC.

In one design, each of DC/DC converters 150-160 is configured as shownin FIG. 6. In this example, each of DC/DC converters 150-160, FIG. 4includes inverter 250, FIG. 6, transformer 252 and rectifier 254.Similar to the switch in the buck converter described above, inverter250 is triggered by controller 80, FIG. 4 to modulate each of DC/DCconverters 150-160 and convert the high voltage DC on lines 103-113,FIG. 4 to the low voltage DC on lines 98-106.

In a preferred embodiment, controller 80 initiates the signals on lines220-230 that are equally time staggered, e.g., staggered 60° apart inphase for the six parallel DC-DC sources 150-160, or 360°/N for Nparallel units, to stagger the timing of the switch or inverter in eachof DC/DC sources 150-160 described above to reduce the ripple of the lowvoltage DC on line 90.

Controller 80 can also determine a desired output voltage to be outputby the power supply module on line 90 based on the current output by thepower supply module by feedback line 93. Controller 80 includesswitching voltage regulator 92 that compares the desired system outputvoltage on low voltage DC bus 60 by feedback line 95 with the actualvoltage output by the power supply module on line 90. Switching voltageregulator 92 then adjusts the voltage output of the power supply moduleto the desired system voltage output by changing the modulation of DC/DCconverters 150-160 using fixed clock modulation (e.g., pulse widthmodulation), self-oscillating modulation, e.g., pulse frequencymodulation or hysteretic modulation, or any modulation technique knownto those skilled in the art.

In one embodiment, controller 80 is also responsive to a fault signal onfeedback line 93 and is programmed to open the switch (e.g., switch 86,FIG. 5), or inverter (e.g., inverter 250, FIG. 6) of each of the DC/DCconverters 150-160, FIG. 4, when the fault signal on line 93 indicatesthe power supply module is generating excessive voltage or current(discussed in detail below). This will remove the malfunctioning powersupply module from the parallel configuration of power supply modules66-76, FIG. 3 of power supply 64 and hence prevent the damaged powersupply module from effecting the operation of power supply 64.Controller 80, may also generate an error signal on line 108 thatenables an external controller, such as a PLC, in response to the faultsignal on line 112 from the various subsystems within the power supplymodule. For example, fault determination circuitry 110 may be responsiveto cooling system 113 that detects an overheating condition in the powersupply module and thus activates fault determination circuitry 110 togenerate a fault signal on line 112 that enables controller 80 togenerate an error signal on line 108 to enable the external controller.Additional auxiliary system 114 can also generate an error signal online 116 that enables fault determination circuitry 110 to generate afault signal on line 112 and enable controller 80 to generate an errorsignal to enable the external controller.

FIG. 7, where like parts have been given like numbers, shows oneembodiment of controller 80 of this invention that utilizes pulse widthmodulation to adjust the low voltage DC output of each of power supplymodules 66-76, FIG. 3. In this example, comparator 119, FIG. 7 comparesa reference system output voltage, V_(set), indicated at 120, e.g., thevoltage on the low voltage DC bus discussed above, to the measuredoutput voltage of the power supply module, V_(meas), indicated at 122,and generates an error signal on line 124. Controller 80 also includescomparator 139 that measures the output current of the power supplymodule, I_(meas), indicated at 126. The measured current, I_(meas) online 140, can take one path through large resistor 143, e.g., about 150kΩ, and is combined with the error signal on line 124 to provide atrimmed and adjusted error signal on line 130 that provides only aslight change in the voltage output of the power supply module. Thisadjustment causes the output voltage of the power supply module to shiftover a narrow range of values and is used to vary the output voltage ofthe power supply module to create the effect of a small positiveinternal impedance. The trimmed and adjusted signal on line 130establishes a synthetic V-I characteristic, as shown by curve 169, FIG.8. The trimmed and adjusted signal provides the power supply module withan apparent, battery-like source-resistance or “pseudo-impedance”corresponding to a small, but positive value of internal resistance,indicated by arrow 190 that enables the power supply module, e.g., powersupply module 66, FIG. 3, to share loads equally with the other powersupply modules, e.g., power supply modules 68-76 of power supply 64.

The measured current, I_(meas), indicated at 126, FIG. 7, also takesanother path on line 180 that includes zener diode 182 and smallresistor 184, e.g., about 301Ω. During operation, zener diode 182remains off. However, if higher than allowable current begins to bedrawn by the power supply module, the current, I_(meas), increases andzener diode 182 will be enabled. At this point, small resistor 184strongly drags the signal voltage down. This results in a large andrapid change in the trimmed and adjusted error signal on line 130 and aradical reduction in the commanded local output voltage set point. Theresult is a sudden and steep drop-off of the V-I curve 169, FIG. 8, asindicated by arrow 194. This feature guarantees that if the current ofan individual power supply module starts to become too high, the outputvoltage of power supply module will drop rapidly and shut that powersupply module down.

Switching voltage regulator 92, FIG. 7 is responsive to the trimmed andadjusted error signal on line 130 and adjusts the output voltagegenerated by each of the DC/DC converters 150-160, FIG. 4, usingmodulation, e.g., fixed clock modulation, such as pulse width modulation(although any type of modulation as discussed above may be utilized).Switching voltage regulator 92 typically includes voltage controlleddelay generator 134, processor 145, switch 162, e.g., a FET, capacitor164, pull-up resistor 166 and voltage source 168. In operation, voltagecontrolled delay generator 134 is held in an inhibited state by thevoltage on capacitor 164. Discharging of capacitor 164 enables voltagecontrolled delay generator 134 to process the trimmed and adjusted errorsignal on line 130 to enable processor 145 by line 143. Discharging ofcapacitor 164 is achieved by a reset signal on line 163 that enables FET162 to discharge capacitor 164 by ground 169. Charging of capacitor isachieved by voltage source 168, as known by those skilled in the art.The trimmed and adjusted error signal on line 143 enables processor 145to generate pulse width signals on lines 220-230, indicated by arrow170, to control the timing of the switches of DC/DC converters 150-160,FIG. 4, as discussed above. Based on the size of error signal on line130, processor 145 determines the pulse width that is needed by thesignals on lines 220-230 to control the timing of the switch of each ofDC/DC converters 150-160, FIG. 4, to adjust the output voltage of thepower supply module to the desired system output voltage. Processor 145,FIG. 7, also determines the sequencing of the pulse signals on lines220-230 to stagger the triggering of the switches or inverters of DC/DCconverters 150-160 to reduce ripple. For example, processor 145, caninitiate a sequence of pulses, shown by arrow 170, that stagger thetriggering of the switches or inverters of the six DC/DC converters150-160, FIG. 4, to reduce ripple. Typically, the staggered pulsesignals on lines 220-230 are in a time staggered sequence 60° apart inphase for the six DC sources 150-160, as described above.

The “pseudo” impedance described above in relation to controller 80,FIGS. 4, 7, and 8 provides desirable load sharing of power supplymodules 66-76, FIG. 3. In this embodiment, if an individual power supplymodule of power supply modules 66-76, of power supply 64 is lightlyloaded compared to the other power supply modules, that power supplymodule will operate at a slightly higher output voltage (due to itspositive “pseudo-impedance”). Conversely, the output voltage for anindividual power supply module of power supply modules 66-76 will beslightly lower when a heavier current is being drawn from it. The highervoltages of lightly loaded power supply modules will result in morecurrent being drawn from them, which will have the effect of reducingtheir output voltage. The more highly loaded power supply modules willdraw less currents, increasing their output voltage. In this way, all ofthe modules will reach an equilibrium in the middle of the voltagerange, in which power is drawn equally from each module, without anyexplicit control signals required to be passed between the modules. Thisprocess of continuous mutual load adjustment and load sharing guaranteesoverall system stability, and prevents any one supply (or collection ofsupplies) from “hogging” the load.

In a preferred embodiment, power supply 64, FIGS. 2 and 3, is ideallyenclosed in a cabinet, such as cabinet 300, FIG. 9. Power supply modules66-76, FIG. 3, are typically each enclosed in a removable drawer, suchas drawer 302, FIG. 9. Removable drawer 302 houses the variouscomponents of the individual power supply modules 66-76 discussed abovein reference to FIG. 4. For example, drawer 302, FIG. 10, includes sixDC/DC converters, of which three are shown and three are stacked below(not shown). The inductors of the buck converters of the shown DC/DCconverters are indicated at 310, 312, and 314. The IGBT switch for eachof the three buck converters is indicated at 316, 318 and 320. The inputcapacitors are indicated at 322, 324, and 326. The controller (shown inphantom) is indicated at 326. Drawer 302 typically includes cooling fans330 that provide cooling air to drawer 302 that exits through exhaustports (not shown) located on back panel 332. The orientation ofinductors 310-314, switches 316-320 and input capacitors 322-326 arearranged to maximize the cooling efficiency of drawer 302.

Drawer 302 typically includes a plurality of different lengthconnectors, e.g., connectors 340, 342, 344, and 346, FIG. 11, that allowthe DC/DC converters to be connected to the high voltage DC bus withoutcausing electrical discharge. In one example, each of the connectors340-348 may include a section of resistive material, such as resistivematerial 352 in connector 346 to prevent discharge of high voltage DCwhen connecting drawer 302 to the high voltage DC bus. In some designsan auxiliary contact connected by a separate auxiliary resistor orspark-suppressing impedance network may be employed to further preventdischarge of high voltage DC when connecting drawer 302 to the highvoltage DC bus. Hence, the configuration of connectors 340-348 allowseach of the various removable drawers that house the power supplymodules to be added, removed, or replaced while a system 30 is inoperation, i.e., the removable drawers are “hot swappable”.

Although specific features of the invention are shown in some drawingsand not in others, this is for convenience only as each feature may becombined with any or all of the other features in accordance with theinvention. The words “including”, “comprising”, “having”, and “with” asused herein are to be interpreted broadly and comprehensively and arenot limited to any physical interconnection. Moreover, any embodimentsdisclosed in the subject application are not to be taken as the onlypossible embodiments. Other embodiments will occur to those skilled inthe art and are within the following claims.

In addition, any amendment presented during the prosecution of thepatent application for this patent is not a disclaimer of any claimelement presented in the application as filed: those skilled in the artcannot reasonably be expected to draft a claim that would literallyencompass all possible equivalents, many equivalents will beunforeseeable at the time of the amendment and are beyond a fairinterpretation of what is to be surrendered (if anything), the rationaleunderlying the amendment may bear no more than a tangential relation tomany equivalents, and/or there are many other reasons the applicant cannot be expected to describe certain insubstantial substitutes for anyclaim element amended.

1. A more compact and higher reliability power supply module comprising:a high voltage DC input; a low voltage DC output; a number of DC/DCconverters connected in parallel between the high voltage DC input andthe low voltage DC output; and a controller configured to modulate eachDC/DC converter to convert the high voltage DC input to the low voltageDC output.
 2. The power supply module of claim 1 in which each DC/DCconverter is configured as a buck converter with a switch cycled by thecontroller to modulate the DC/DC converter.
 3. The power supply moduleof claim 1 in which each DC/DC converter includes an inverter, atransformer and a rectifier in which the inverter is cycled by thecontroller to modulate the DC/DC converter.
 4. The power supply moduleof claim 2 in which the controller is configured to stagger thetriggering of the switch of each DC/DC converter to reduce ripple on thelow voltage DC bus.
 5. The power supply module of claim 3 in which thecontroller is configured to stagger the triggering of the inverter ofeach DC/DC converter to reduce ripple on the low voltage DC bus.
 6. Thepower supply module of claim 1 in which the controller is configured tomodulate each DC/DC source to control output voltage or current.
 7. Thepower supply module of claim 2 in which the controller is responsive toa fault signal input and programmed to open the switch of each DC/DCconverter in response to the fault signal.
 8. The power supply module ofclaim 3 in which the controller is responsive to a fault signal inputand programmed to open the inverter of each DC/DC converter in responseto the fault signal.
 9. The power supply module of claim 1 in which thecontroller is further configured to output an error signal in responseto a fault signal.
 10. The power supply module of claim 1 in which thepower supply module includes a fuse between the plurality of DC/DCconverters and the low voltage DC bus designed to fail at a currentlevel greater than the rated current output of the power supply module.11. The power supply module of claim 1 in which the controller isconfigured to determine a desired output voltage based on the currentoutput by the power supply module.
 12. The power supply module of claim11 in which the controller includes a switching voltage regulatorconfigured to compare a desired system output voltage with the voltagelevel output by the power supply module and to adjust the voltage outputby each DC/DC converter such that the output of the power supply moduleapproximately equals the desired system output voltage.
 13. The powersupply module of claim 12 in which the switching voltage regulatoradjusts the voltage output by each of the DC/DC converters bymodulation.
 14. The power supply module of claim 1 in which thecontroller of the power supply module utilizes pseudo-impedance toprovide autonomous load sharing with other power supply modules.
 15. Thepower supply module of claim 1 in which the low voltage DC output is inthe range of about 6V DC to 100V DC.
 16. The power supply module ofclaim 15 in which the low voltage DC output is about 48V DC.
 17. Thepower supply module of claim 9 further including a fault determinationcircuit for generating the fault signal.
 18. The power supply module ofclaim 17 further including a cooling system for cooling the powermodule.
 19. The power supply module of claim 17 in which the faultdetection circuit generates a fault signal when the power supply moduleexceeds a predetermined temperature.
 20. The power supply module ofclaim 2 in which the buck converter includes an input capacitor, aninductor, an output capacitor and the switch.
 21. The power supplymodule of claim 1 in which the power supply module is configured in aremovable drawer.
 22. The power supply module of claim 21 in which theremovable drawer is disposed in a cabinet configured as a power sourcesystem.
 23. The power supply module of claim 22 in which each removabledrawer includes a plurality of different length connectors thatelectrically connect the number of DC/DC converters of the power supplymodule to the high voltage DC bus at different times to reduceelectrical discharge.
 24. The power supply module of claim 23 in whichthe removable drawer can be removed, replaced, or added to the powersource system while the power source system is operating.
 25. The powersupply module of claim 23 in which each of the connectors includes aresistive material for reducing electrical discharge when connecting thepower supply module to the high voltage DC bus.
 26. The power supplymodule of claim 22 in which each removable drawer includes an auxiliarycontact connected by a separate auxiliary resistor or spark-suppressingimpedance network to reduce electrical discharge.
 27. A more compact andhigher reliability power supply module comprising: a high voltage DCinput; a low voltage DC output; a number of DC/DC converters connectedin parallel between the high voltage DC input and the low voltage DCoutput; and a controller configured to modulate each DC/DC converter toconvert the high voltage DC input to the low voltage DC output, whereineach DC/DC converter is configured as a buck converter with a switchcycled by the controller to modulate the DC/DC converter.
 28. The powersupply module of claim 27 in which the controller is configured tostagger the triggering of the switch of each DC/DC converter to reduceripple on the low voltage DC bus.
 29. A more compact and higherreliability power supply module comprising: a high voltage DC input; alow voltage DC output; a number of DC/DC converters connected inparallel between the high voltage DC input and the low voltage DCoutput; and a controller configured to modulate each DC/DC converter toconvert the high voltage DC input to the low voltage DC output, whereineach DC/DC converter includes an inverter, a transformer and a rectifierin which the inverter is cycled by the controller to modulate the DC/DCconverter.
 30. The power supply module of claim 29 in which thecontroller is configured to stagger the triggering of the inverter ofeach DC/DC converter to reduce ripple on the low voltage DC bus.